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2/21/2008 10:46:01 AM EDT
Ive got an A1 upper that I installed night sights on (XS).
The rear sight needs adjusting further to the left than the gun allows.
Im sure the FSB is not lined up correctly, so I have to knock the pins out and adjust it a little.

I would like the rear sight to be in the middle if at all possible. What diection should I bump the FSB?

I am gussing to the right
2/21/2008 4:42:50 PM EDT
[#1]
Does your front site base have tapper pins?
2/22/2008 2:42:43 AM EDT
[#2]
!0 to 1 it's not an off line front sight base; but rather that the barrel is tilted slightly in the upper reciever.

This is a very common problem these days, in large part due to the advent of the plastic reciever holding units to install barrels---instead of the proper installation procedure of clamping the barrel. People are so bloody worried about leaving a smudge on the barrel (under the HGs) that they pay twice as much for a piece of plastic as a pair of barrel vise clamps costs.

When you clamp the upper, the barrel wants to turn to the left in the slot, as the piece is tightened; so the rifle shoots to the right. Remember it only takes a few thousanths of an inch shift at the back of the barrel/reciever to cause a very large shift in POI at the sighting point.

So leave your front sight assy alone until you at least check to make sure the whole barrel isn't slightly tilted.
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